Wearable display devices in the form of eyewear designed to display information on the eyewear's lenses for personal viewing have been undergoing rapid development in the last few years. Sometimes described as augmented reality devices, or smart glasses, the wearable display devices typically employ a camera, a processor and connectivity component, and a small screen on which to display visual information on the eyewear's lens (or lenses). The display of visual information overlays a real object detected in the wearer's field of vision, such as with images and/or text that identify or otherwise augment the viewer's perception of the object.
Wearable display devices have many potential applications. For example, wearable display devices are being specifically designed to provide users with hands free access to information related to their surroundings, such as technicians with technical specifications about the equipment they are operating or servicing, or travelers with navigation aids during their journey. In some applications, wearable display devices are being designed to provide users with hands free access to specific features of the device itself using voice commands or head movements, including such features as taking pictures or videos with the device, or sending messages to other devices.
Touch display devices in the form of smart phones, tablets, laptops or other digital devices are now ubiquitous. As users take their devices with them into public places, the need to secure the devices against unauthorized use becomes more acute. Typically, devices are secured through some sort of device lock that requires the user to enter via the device's touch display interface a secret security code, such as a password, personal identification number or passcode that functions as a key to unlock the device. This allows the user to be authenticated as an authorized user of the device before it is unlocked. However, unlocking the device in a public space renders the secret security code vulnerable to observation attacks.
In addition to being ubiquitous, the use of advanced microprocessors in touch display devices continues to grow, with larger and higher definition display areas to support. The advanced microprocessors, with more transistors and higher frequencies, results in corresponding increases in power and energy consumption. Particularly in mobile devices, such as tablet computers and smart phones etc., increased power consumption can lead to overheating, which can negatively affect performance and significantly reduce battery life. Because batteries typically have a limited capacity, running the processor of a mobile device more than necessary could drain the capacity more quickly than desired.